Method for making cathodes for neon and argon gas filled tubes

ABSTRACT

A method for making gaseous discharge lamp cathodes comprises, in order to perfectly center the cathode with respect to the tube glass envelope, the steps of: (a) narrowing the end portion of the metal cathode near the edge thereof, (b) fully inserting, about the narrowed zone, a circular crown shaped mica small collar and (c) upsetting the edge so as to lock the mica collar in place.

BACKGROUND OF THE INVENTION

The present invention relates to a method for making a new type ofcathode, for gaseous discharge lamps, such as neon or argon gas filledlamps.

As is known, several problems are involved in making gaseous dischargelamps, mainly because of a quick increase of the lamp temperature whichin turn causes a great thermal expansion of the metal cathode and theglass envelope which is susceptible to the easily broken.

In order to at least alleviate the above mentioned problem, the cathodemust be precisely fitted in the tube glass envelope so as to beperfectly centered and insulated.

At present this problem is frequently solved by a method which comprisesthe steps of: (a) engaging a mica spacer collar, of circular crownshape, on the end edge of the metal cathode, (b) locking this micacollar against the end of the cathode by using a longitudinallyperforated steatite plug member and (c) wrapping a mica sheet about thecathode so as to insulate the cathode from the envelope glass.

This known method, however, is very complex and expensive.

SUMMARY OF THE INVENTION

Thus, the main object of the present invention is to solve the abovementioned problem in a very simple way, by providing a very simplemethod for making cathodes for gaseous discharge lamps, in particularneon and argon gas filled lamps, which affords the possibility ofperfectly insulating and centering the cathode in such a lamp.

Another object of the present invention is to provide such a gaseousdischarge lamp cathode making method which provides a new type ofstrong, long duration and unexpensive cathode.

According to one aspect of the present invention, the above mentionedobjects, as well as yet other objects, which will become more apparenthereinafter, are achieved by a method for making cathodes for gaseousdischarge lamps having the features recited in the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention willbecome more apparent hereinafter from the following detailed descriptionof a preferred embodiment thereof which is illustrated, by way of anindicative but not limitative examples, in the accompanying drawings,where:

FIG. 1 is a schematic view illustrating a cathode fitted at the end of aglass tube, for gaseous discharge lamps;

FIG. 2 shows the end portion of the cathode, which has been properlynarrowed; and

FIG. 3 shows the end portion of the cathode with applied a spacer micacollar which is locked in place by upsetting the edge of the cathode.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the figures of the accompanying drawings, the cathodeaccording to the present invention comprises a cylindrical body 1 which,at one end thereof, is provided with a half-ball shaped portion 1' inwhich there are fitted the power supply wires 2, the other end 1" beingopen and adapted to be fitted in the glass tube 3.

The end portion of the cathode, at the open end 1", is subjected,according to the invention, to the following processing steps: (a)narrowing the cathode zone near its edge; (b) fitting a spacer collar 4,made of mica and having a circular crown shape, about the narrowed zone;and (c) upsetting the cathode edge 5 so as to lock the mica collar 4 inplace.

While the invention has been disclosed and illustrated with reference toa preferred embodiment thereof, it should be apparent that the disclosedembodiment is susceptible to several modifications and variations all ofwhich will come within the spirit and scope of the appended claims.

We claim:
 1. A method for making a metal cathode for gaseous dischargelamps, in particular neon and argon gas filled lamps, characterized inthat said method comprises the steps of:(a) narrowing a zone of saidcathode near an edge thereof; (b) fitting, about said narrowed zone, amica collar of circular crown shape; (c) upsetting said edge so as tolock said mica collar in place.
 2. A metal cathode made by a methodaccording to claim 1, characterized in that said cathode comprises acircular crown shaped mica spacer collar fitted about a narrowed zone ofsaid cathode and locked in place by an upset portion.